Liquid crystal display devices are mounted on various apparatuses and devices such as a television receiver, an in-vehicle display, for example, car navigation equipment, a notebook computer, a tablet computer and mobile devices such as a cell phone and a smartphone.
Such liquid crystal display devices employ liquid crystals whose modes vary in accordance with intended purposes.
For example, in a liquid crystal display device which is of a vertical-electric-field type such as a twisted nematic (TN) mode or an optically compensated bend (OCB) mode, the alignment direction of liquid crystal molecules contained in a liquid crystal layer held between a common electrode provided in an upper substrate and pixel electrodes provided in a lower substrate is controlled by an electric field produced between the common electrode and the pixel electrodes.
In a liquid crystal display device which is of a lateral-electric-field type such as an in-plane switching (IPS) mode, a common electrode and pixel electrodes are provided in a single substrate only, and the alignment direction of liquid crystal molecules contained in a liquid crystal layer is controlled by an electric field (fringing field) produced between the common electrode and the pixel electrodes. A liquid crystal display device adapted for a fringe-field switching (FFS) mode which is one mode of the IPS mode can ensure a great aperture ratio, and thus has a high brightness and a superior viewing angle characteristic.
It should be noted that liquid crystal display devices applied to mobile terminals are strongly required to reduce a circuit power consumption. As means for reducing the power consumption, a low-frequency driving is proposed. The low-frequency driving is a drive in which the drive frequency of a liquid crystal display device is reduced to, for example, ½ or ¼ of the drive frequency of a drive to be performed under standard conditions, to thereby reduce a circuit power consumption. The low-frequency driving is not suitable for displaying of moving images, since the intervals at which an image signal is written to a pixel electrode are long. On the other hand, in the case of displaying a still image, for example, in a display operation in which importance is not attached to visibility of moving images, the low-frequency driving is an advantageous countermeasure for reducing the circuit power consumption. However, in the case where the low-frequency driving is performed in a liquid crystal display device, it is necessary to reduce flicker.